unvented cylinder drip through tundish

[bawbster]

Moved house few days back and have 7 days to report any faults. Whilst checking on the unvented cylinder to check for leaks (had previous on leaking UC), after about 20 minutes of hot water on a single drip can be seen every 30 - 40 seconds until the hot water is turned off.
Is this something that requires attention or is it meant to do this. Bought a new build about 9 years back with a similar setup and tge site foreman said if drips, it's nothing to worry about but if it flows get it sorted ASAP.
Cheers for any help.

Was told the boiler was serviced recently but don't know if the cylander was done.

 

[Lower]

If its dripping from the tundish there is something wrong with the expansion vessel or bubble. It may have an internal airgap that just needs replenishing. Is there a white metal expansion vessel attached to it? If yes, if probably needs servicing. If no, then it may well have instructions for how to reestablish the bubble printed on the outside of the cylinder and you can do it yourself.

 

[bawbster]

Got it sorted, engineer replaced the expansion vessel but after about 6 hours or so can hear dripping but no evidence of any leaks coming from anywhere. This was without hot water being on.
cheers